feat(gcp): Add span streaming support to GCP Cloud Functions integration

[ericapisani]

Migrate GCP integration to support spans-first tracing via the span streaming API.
The integration now supports both:

• Span streaming (new trace lifecycle)
• Traditional transaction-based approach (fallback)

Add request attributes to spans including headers, HTTP method, and query string.
Include cloud provider context and segment source in span metadata.

Add comprehensive tests for span streaming functionality including error handling,
trace context propagation, and PII filtering for query strings.

Fixes PY-2324 and #6022

[linear-code]

PY-2324

[github-actions]

Codecov Results 📊

✅ 446 passed | Total: 446 | Pass Rate: 100% | Execution Time: 1m 9s

📊 Comparison with Base Branch

Metric	Change
Total Tests	—
Passed Tests	—
Failed Tests	—
Skipped Tests	—

✨ No test changes detected

All tests are passing successfully.

❌ Patch coverage is 0.00%. Project has 14925 uncovered lines.
❌ Project coverage is 34.84%. Comparing base (base) to head (head).

Files with missing lines (1)

File	Patch %	Lines
sentry_sdk/integrations/gcp.py	0.00%	⚠️ 19 Missing

Coverage diff

@@            Coverage Diff             @@
##          main       #PR       +/-##
==========================================
- Coverage    34.86%    34.84%    -0.02%
==========================================
  Files          190       190         —
  Lines        22890     22906       +16
  Branches      7834      7842        +8
==========================================
+ Hits          7981      7981         —
- Misses       14909     14925       +16
- Partials       829       829         —

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Generated by Codecov Action

[sentry-warden]

Unhandled UnicodeDecodeError in query_string.decode() crashes GCP function invocations

If gcp_event.query_string contains non-UTF-8 bytes (e.g. ?q=foo%80bar), the .decode("utf-8") call raises an unhandled UnicodeDecodeError that propagates outside the try/except block and the capture_internal_exceptions context, causing the entire GCP function invocation to fail due to Sentry instrumentation. Use decode("utf-8", errors="replace") to be safe.

Evidence

• Lines 103–106 are outside the with capture_internal_exceptions(): block (which ends after timeout_thread.start()) and outside the try/except Exception block that starts only inside with span_ctx:.
• A UnicodeDecodeError thrown here escapes the with sentry_sdk.isolation_scope() context manager entirely and propagates back to the GCP framework.
• The existing event processor at line 223–224 does the same decode, but it runs inside a registered event processor callback which Sentry wraps with capture_internal_exceptions internally.
• The new span-streaming code path at lines 103–106 has no such protection, making it a new failure mode introduced by this diff.

Suggested fix: Use errors='replace' to avoid crashing on malformed query strings.

Suggested change

	if should_send_default_pii() and hasattr(gcp_event, "query_string"):
	additional_attributes["url.query"] = gcp_event.query_string.decode(
	"utf-8"
	)
	additional_attributes["url.query"] = gcp_event.query_string.decode(
	"utf-8", errors="replace"
	)

_{Identified by Warden find-bugs · 6FG-4J5}